Killing your spouse's lover "in the heat of passion" used to be a mitigating circumstance. But despite her assertion that she brought a kitchen knife with her to kill herself, I find it very difficult to believe that this was not a premeditated killing.
Contrast this with the farmer who defended his home by shooting a burglar who threatened his life, and was given a sentence of life in prison for it.
Justice in England is very badly distorted.
"Justice in England is very badly distorted."
That may or may not be the case, but I am always wary of second guessing the decision of a jury when they have had the opportunity to listen to all the evidence, arguments for both sides and all I have is a news summary.
That's the case here and is the case in the Tony Martin case that you reference. In that case Martin was found guilty by a jury that had heard all the evidence, a verdict that was confirmed on appeal. He wasn't, though 'given a life sentence for shooting a burglar who threatened his life' as you say - if the jury had found that to be the case they would have acquited (on the murder charge in any case, I believe there were other charges based on the fact that Martin's guns were not licenced). The facts as established by the jury was that Martin shot the burglar in the back while he was running away from the property, having been disturbed, and was not posing any threat to Martin's life. That was why he was convicted.